<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
  <meta charset="UTF-8">
  <title>JS改变HTML样式（css）</title>
</head>
<body>
<p id="demo">JavaScript 能够改变 HTML 元素的样式。</p>
<button
        onclick="document.getElementById('demo').style.fontSize='35px'">点击我</button>
</body>
</html>